Rear suspension system for bicycles

ABSTRACT

A rear suspension system for bicycles, such as freeride, downhill and trail-style mountain bikes. The suspension system includes a rear suspension for coupling the rear wheel of the bicycle to the bicycle frame, a rear shock absorber disposed entirely in front of the seat tube of the frame and a linkage for operatively coupling the rear suspension to the rear shock absorber. The linkage intersects the longitudinal axis of the seat tube for transmitting rear suspension forces around the seat tube to the rear shock absorber. The seat tube is preferably continuous and is disposed so that the bicycle seat is adjustable over a full range of seat positions. Additionally, the seat tube and rear suspension system are configured so that the rear wheel and rear suspension will not contact the seat tube, seat, or bicycle rider even when the rear suspension system is in a fully compressed, forward position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 14/177,001,filed Feb. 10, 2014, pending, which is a continuation of applicationSer. No. 13/158,238, filed Jun. 10, 2011, now U.S. Pat. No. 8,646,797,issued Feb. 11, 2014, which is a divisional of application Ser. No.12/046,303, filed Mar. 11, 2008, now U.S. Pat. No. 7,980,579, issuedJul. 19, 2011, which is a continuation of application Ser. No.11/008,260, filed Dec. 10, 2004, now U.S. Pat. No. 7,467,803, issuedDec. 23, 2008, which claims the benefit of the filing date of U.S.Provisional Application No. 60/528,725, filed Dec. 12, 2003. Thedisclosure of each of the previously referenced U.S. patent applicationsand patents (if applicable) is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

This application relates to an improved rear suspension system forbicycles.

BACKGROUND

High-end mountain bikes typically have both rear and front suspensionsystems to assist in traversing uneven terrain. This is particularly thecase for freeride, downhill and trail bikes which are designed todescend steep and uneven mountain terrain, often at high speeds. Manyrear suspension systems designed for freeriding and other bikingapplications are known in the prior art. Such systems generally includea rear suspension permitting a limited degree of travel of the rearwheel relative to the bicycle frame and a rear shock absorber forabsorbing suspension forces. The range of rear wheel travel that ispermitted by existing suspension systems varies, but is typically withinthe range of about 5 to 12 inches measured vertically (although somedesigns permit travel outside this range).

While many mid and long rear wheel travel bicycle designs are known,most designs have rear suspension systems which compromise overall bikeperformance and versatility. Two primary problems caused by existingdesigns are (a) undesirable contact between the rear tire or suspensionlinkages and the bicycle seat or seat tube when the rear suspensionsystem is under full compression; and (b) a restricted range ofadjustability of the seat position.

U.S. Pat. Nos. 5,509,679, 5,678,837 and 5,899,480 owned by SpecializedBicycle Components, Inc. of Morgan Hill, Calif. describe two primarytypes of four bar linkage rear suspension systems, commonly referred toas the walking beam and low linkage designs. The above-noted patents areincorporated herein by reference in their entireties. The walking beamdesign is illustrated in FIG. 1 and includes a rocker arm link extendingin a near horizontal orientation and a rear shock absorber having atravel axis extending in a near vertical orientation. The rocker armlink pivots on the seat tube portion of the bicycle frame and extendsbetween an upper end of the rear shock absorber and an upper end of theseat stays. The main manufacturing advantages of the walking beam designare that the frame of the bike can be built out of a typical “triangle”shape, common in the bicycle industry, the pivot point for the rockerarm link can be conveniently arranged to mount to the seat tube, and therear shock can be conveniently pivotally connected to the top of thebottom bracket area. The main performance advantage of the walking beamdesign is that the seat tube is straight and continuous and allows for afull adjustment range of the seat (i.e., saddle) height. This isimportant because the seat needs to be raised to the correctbiomechanical position to allow for effective pedaling performance whenclimbing up hills and crossing non-technical terrain and the seat needsto be lowered substantially (typically by 4 to 8 inches or moredepending upon the rider's height and body proportions) so that therider can safely and effectively traverse difficult or challengingterrain and obstacles.

The walking beam design is suitable for bicycle suspension frames withup to approximately 6 inches of vertical rear wheel travel. However, asthe rear travel gets longer than about 6 inches, several problems arisewith the walking beam design. As the rear wheel travel path starts tocome forwards, towards the front of the bike, this movement combinedwith the generally rearward sloping seat tube causes the rear wheel andthe seat tube to collide before the rear wheel has finished its travel.Further, the relatively high linkage arrangement (when compared to thelow linkage four bar design described below) causes the rocker arm link(when the rear suspension is under substantial or full compression) tointerfere with the low rearward position of the rider's “bottom” (aposition needed to ride challenging terrain) and also the rear seat whenthe seat is lowered.

Longer travel suspension frames work better with rear shock absorberstroke length ratios that match their travel. If the ratio of rear wheeltravel versus shock stroke length increases beyond a favourable ratio,then the relatively short stroke shock absorber will be less effectivein its ability to control the movement of the rear suspension and willbe potentially more prone to failure. Additionally, higher rear shockabsorber spring rates are required, which reduces the “suppleness” ofthe rear suspension's feel. As the rear wheel's travel increases, therocker arm link pivot must also be moved up “higher” along the seattube, to accommodate the longer stroke rear shock absorber (which isfixed near the bottom bracket of the front triangular frame as shown inFIG. 1). Additionally, the rocker arm link needs to be longer toaccommodate the greater length of the shock absorber stroke. Thisexacerbates the problems discussed above concerning the interference ofthe rear wheel and rocker arm link with the frame's seat tube, seat, andthe rider's bottom. These effects are increased even more in the case ofsmaller frame sizes designed for smaller riders, because there is lessroom for the suspension elements to move due to a seat that is in anoverall lower position (because the rider is smaller).

Low linkage four bar rear suspensions as exemplified by the SpecializedFSR design shown in FIG. 2 also exhibit several limitations. On the onehand, such low linkage designs do not suffer from rear wheel and rockerarm link interference issues as described above in connection with thewalking beam configuration. This is because the rocker arm link istypically mounted in a lower, diagonal to near vertical position, andthe rear shock absorber is mounted in a diagonal to near horizontalposition (FIG. 2). Additionally, the seat tube position can bearbitrary, as it is typically mounted to the end of a cantilevered“beam”, instead of being welded in line with the bottom bracket axis.However, on the other hand the low linkage design requires that the rearshock “interrupt” the seat tube and hence causes the seat tube to be cutoff at the shock absorber location. This severely limits the range ofseat and seat post adjustability. This is a major problem on bikesdesigned for technical riding where the seat needs to be substantiallylowered so that it is out of the way of the rider's body movement, suchas when traversing uneven downhill terrain. To get the seat low enough,technical riders typically cut their seat post to a shorter length.However, this leaves the seat post too short and the seat cannot beraised enough to provide a biomechanically correct pedaling position forthe rider, particularly when climbing hills. A full range of adjustableseat post positions is desirable for the reasons specified above.

Other existing rear suspension systems designed for technical riding,such as single pivot swing arm and virtual pivot point designs, alsosuffer from various drawbacks. For example, rear suspensions having longswing arms typically have lower overall lateral rigidity than otherdesigns. Some long travel virtual pivot point designs includeinterrupted seat tubes, or have full length seat tubes which are bent toprovide sufficient rear wheel clearance, but such designs restrict therange of seat height adjust-ability. Other four bar virtual pivot pointdesigns have elongated seat stays which extend past the seat tube toallow for a full length seat tube. However, increasing the length of theseat stays also sacrifices the overall lateral stability of the rearsuspension system which is not desirable.

The need has therefore arisen for an improved rear suspension system forbicycles which maintains the advantages of prior art designs whileeliminating or substantially reducing their disadvantages.

SUMMARY

In accordance with the invention, a rear suspension system for a bicyclehaving a rear wheel and a frame is provided. The frame includes a seattube having a longitudinal axis. The system includes a rear suspensionpivotally coupling the wheel to the frame; a rear shock absorberdisposed entirely forwardly of the seat tube; and a linkage coupling therear suspension to the shock absorber for transferring forcestherebetween, wherein the linkage extends in an orientation intersectinga plane passing through the seat tube parallel to the longitudinal axis.

The linkage is configured to transmit the suspension forces around theseat tube. In one embodiment the linkage may straddle the seat tube. Forexample, the linkage may comprise first and second linkage elementsdisposed on opposite sides of the seat tube. The linkage preferably hasa length exceeding the diameter of the seat tube and is pivotablycoupled to both the rear suspension and the shock absorber. In oneembodiment the rear suspension may include one or more pivot points,where the most forward one of the pivot points is located rearwardly ofthe longitudinal axis.

Preferably the seat tube of the bicycle frame is continuous and theshock absorber has first and second ends coupled to the frame forwardlyof the seat tube. In one embodiment the first end of the shock absorberis pivotably coupled to the frame and the second end of the shockabsorber is pivotably coupled to the linkage. In one particularconfiguration, the frame comprises a top tube, a head tube and a downtube in addition to the seat tube, and the first and second ends of theshock absorber are coupled to the down tube.

In one embodiment, the bicycle frame is orientable in a vertical planeand the shock absorber may be supported so that its longitudinal axisextends in a plane at an angle of between about 45-90° relative to thevertical plane. In one embodiment the shock absorber may extend in ahorizontal or near-horizontal orientation to maximize its stroke length.In a particular embodiment the shock absorber may extend beneath andparallel to a top tube of the bicycle frame.

In one particular embodiment, the rear suspension may comprise a fourbar suspension design including a chain stay link and a seat stay linkcoupled to the rear wheel and a rocker arm link coupled to the seat staylink and extending forwardly therefrom. In one embodiment the linkage iscoupled to the rocker arm. In alternative embodiments the linkage isalternatively coupled to the seat stay link or the chain stay link.

The suspension system is particularly useful to mid to long rear wheeltravel bicycle designs where the range of vertical travel of thesuspension system exceeds approximately 5 inches.

The application also relates to a bicycle having a rear wheel and aframe orientable in a vertical plane, the frame comprising a seat tubehaving a longitudinal axis. The bicycle further includes a rearsuspension for pivotally coupling the rear wheel to the frame, whereinthe rear wheel is movable within a range of travel between a mostrearward position and a most forward position. The bicycle furtherincludes a rear shock absorber disposed entirely forwardly of the seattube and a linkage coupling the rear suspension to the rear shockabsorber, wherein the linkage extends in an orientation intersecting aplane passing through the seat tube parallel to the longitudinal axis.

Preferably the rear wheel and the rear suspension system are spacedapart from the seat tube in the most forward position and thelongitudinal axis of the seat tube extends at an angle substantiallytangential to the most forward position of the rear wheel. In oneembodiment the longitudinal axis of the seat tube extends at an anglebetween about 50-75° degrees relative to a horizontal plane passingthrough the seat tube and extending perpendicular to the vertical plane.More preferably, the longitudinal axis of the seat tube extends at anangle of between about 55-65° degrees relative to the aforesaidhorizontal plane.

The seat tube of the frame is preferably continuous. The frame may alsoinclude a down tube and a bottom bracket mounted at a lower end of saiddown tube for receiving a crank assembly of the bicycle. The bottom endof the seat tube is offset forwardly as compared to conventional framedesigns such that the longitudinal axis of said seat tube intersects thedown tube at a location forward of the bottom bracket.

The invention may also relate to a kit for coupling a rear suspension toa shock absorber using the linkage of the applicant's invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention, but whichshould not be construed as restricting the spirit or scope of theinvention in any way.

FIG. 1 is a side elevational view of a rear suspension system of theprior art configured in a walking beam four bar subassembly.

FIG. 2 is a side elevational view of a rear suspension system of theprior art configured in a low linkage four bar subassembly.

FIG. 3 is a side elevational view of a bicycle having the rearsuspension system of the invention.

FIG. 4 is an enlarged side elevational view of the applicant's rearsuspension system of FIG. 3.

FIG. 5(a) is an enlarged rear isometric view of the applicant's rearsuspension system of FIG. 3 in an uncompressed configuration.

FIG. 5(b) is an enlarged isometric view of the applicant's rearsuspension system of FIG. 3 under full compression.

FIG. 6 is a schematic view showing the relative orientation of thebicycle subframe and rear suspension system of FIGS. 3-5 when thesuspension system in a fully compressed configuration.

FIG. 7 is a schematic view showing the bicycle subframe and rearsuspension of FIGS. 3-5 when the suspension system is in an uncompressedconfiguration.

FIG. 8 is a schematic view showing the relative orientation of thebicycle subframe and rear suspension system in an alternative embodimentof the invention.

FIG. 9 is a schematic view showing the relative orientation of thebicycle subframe and rear suspension system in a further alternativeembodiment of the invention.

FIG. 10 is a schematic view showing the relative orientation of thebicycle subframe and rear suspension system in a further alternativeembodiment of the invention.

DETAILED DESCRIPTION

Throughout the following description, specific details are set forth inorder to provide a more thorough understanding of the invention.However, the invention may be practiced without these particulars. Inother instances, well known elements have not been shown or described indetail to avoid unnecessarily obscuring the invention. Accordingly, thespecification and drawings are to be regarded in an illustrative, ratherthan a restrictive, sense.

This application relates to a bicycle 10 having an improved rearsuspension system 12 (FIG. 3). Bicycle 10 includes a rear wheel 14, afront wheel 16 and a frame 18 coupled to wheels 14, 16 for supporting arider. As described in detail below, rear suspension system 12 pivotablycouples rear wheel 14 to frame 18. Front wheel 16 is coupled to frame 18by means of front forks 20. Forks 20 may optionally include front shockabsorbers 21.

As used in this patent application, the terms “front”, “forward”, andforwardly” mean toward the front end of bicycle 10 and the terms “rear,“rearward”, and rearwardly mean toward the rear end of bicycle 10.Similarly, the words “top”, “upper”, “upward” and “upwardly” mean towardthe upper portion of bicycle 10 when it is in an ordinary ridingorientation with wheels 14, 16 resting on a support surface, as shown inFIG. 3. The words “bottom”, “lower”, “loward” and “lowardly” refer tothe lower portion of bicycle 10 when it is in the ordinary ridingorientation.

In the illustrated embodiment, bicycle frame 18 has a generallytriangular configuration and comprises a top tube 22, a down tube 24 anda seat tube 26. Frame 18 also includes a head tube 28 for receivingforks 20 and handlebars 30 at the front end of bicycle 10. A seat post32 supporting a seat 34 is slidably coupled to seat tube 26. Theposition of seat post 32 is adjustable to alter the height of seat 34.Although the present invention is described with reference to thetriangular-shaped frame 18 of FIG. 3, the invention is equallyapplicable to other frame designs, including monocoque frames (such asis shown in FIG. 2).

Bicycle frame 18 further includes a bottom bracket 35 located at thebottom end of down tube 24 for receiving a pedal assembly (not shown)including a crank arm and bottom bracket axle. Most conventional bicycleframes having a triangular configuration have a seat tube which iscoincident with the bottom bracket as shown in FIG. 1 (i.e., thelongitudinal axis of the seat tube intersects the bottom bracket).However, in the Applicant's invention, the position of seat tube 26 isshifted forwardly so that the axis of seat tube 26 intersects down tube24 at a location spaced forwardly and upwardly from bottom bracket 35.This feature is described in further detail below. The Applicant's frame18 may further include a bottom bracket block 37 for supporting bottombracket 35 and elements of rear suspension system 12 at a locationrearwardly of seat tube 26.

Rear suspension system 12 is illustrated in detail in FIGS. 4 and 5.System 12 may include a rear suspension 40, a rear shock absorber 42 anda linkage 44 for coupling rear suspension 40 to shock absorber 42.Linkage 44 enables transfer of forces around seat tube 26 betweensuspension 40 and shock absorber 42 as discussed in detail below.

In the illustrated embodiment, rear suspension 40 is configured in aconventional low linkage four bar arrangement. Such an arrangement isdescribed in detail in U.S. Pat. Nos. 5,509,679, 5,678,837 and 5,899,480which are incorporated herein by reference, as indicated above. In thisarrangement, rear suspension 40 includes a chain stay link 46, a seatstay link 48 and a rocker arm link 50 which, together with frame 18,define a four bar linkage. More particularly, chain stay link 46includes spaced-apart first and second arms 47 which straddle rear wheel14 when bicycle 10 is assembled (FIG. 3). A yolk-shaped first end 52 ofchain stay arms 47 is pivotably coupled to bottom bracket block 37 offrame 18 by means of a pivot 56. A second end 58 of each chain stay arm47 is pivotably coupled to a drop-out bracket 60 by means of a pivot 62.Drop-out bracket 60 supports axle 64 and hub 65 of rear wheel 14 (FIGS.5(a) and 5(b)). In the embodiment of FIG. 3-5 pivot 62 is thereforespaced a short distance forwardly of the axis of axle 64 and hence thecenter of rear wheel 14 (in the schematic views of FIGS. 6-10 reference64 denotes the center of wheel 14).

Seat stay link 48 includes spaced-apart arms 49 which also straddle rearwheel 14 when bicycle 10 is assembled. A first end 66 of each seat stayarm 49 is coupled to a corresponding drop-out bracket 60 and a secondend 68 of each seat stay arm 49 is coupled to rocker arm link 50 bymeans of a pivot 70. In the illustrated embodiment rocker arm link 50includes spaced-apart arm elements 51 which are connected together at afirst end 72 thereof by a seat stay arch 53. Seat stay arch 53 extendstransversely between arm elements 51 in the vicinity of pivots 70. Eachrocker element 51 also has a second end 74 pivotably coupled to bottomblock 37 of frame 18 by means of a pivot 76. As shown best in FIGS. 5(a)and 5(b), pivot 76 is located proximate seat tube 26 and above a pivot56.

Rear suspension 40 illustrated in FIGS. 3-5 thus includes four separatepivot points, namely pivots 56, 62, 70 and 76. This arrangement enablesrear wheel 14 to pivot relative to bicycle frame 18 between a rearposition (FIG. 5(a)) when traveling over flat terrain and a raisedforward position (FIG. 5(b)) to accommodate uneven terrain. The maximumamount of travel of rear wheel 14 permitted by rear suspension 40 mayvary, but is typically in the range of 5-10 inches measured vertically.Unlike conventional single pivot suspension designs, rear suspension 40has multiple pivot points and is therefore not constrained to follow aconstant arc pivoting wheel path. Rather, as will be appreciated by aperson skilled in the art, suspension 40 exhibits the advantages ofother known four bar suspension geometries in terms of pedal-inducedsuspension movement, acceleration, pedal feedback and brakingcharacteristics.

As will also be appreciated by a person skilled in the art, the drawingsillustrate only one example of a rear suspension 40, namely a lowlinkage four bar configuration, and many other types of suspensionsystems could be substituted without departing from the invention,including walking beam four bar linkages, virtual pivot point designsand single pivot swing arm designs.

As indicated above, rear suspension system 12 also includes a rear shockabsorber 42 for absorbing forces received from rear suspension 40 vialinkage 44. In the Applicant's invention shock absorber 42 is positionedentirely forwardly of seat tube 26. In the illustrated embodiment, shockabsorber 42 extends along an axis substantially parallel to top tube 22.This orientation is sometimes referred to in the bicycle industry as a“horizontal” orientation as opposed to a “vertical” orientation asexemplified by the walking beam design shown in FIG. 1. However, neitherorientation is precisely “horizontal” or “vertical” and many variationsare possible. One advantage of orientating shock absorber 42 parallel totop tube 22 is that the length of shock absorber 42 may be maximized(i.e., there is sufficient available space to accommodate relativelylarge, long stroke length shock absorbers 42). There are also advantagesto isolating shock absorber 42 from the effects of side loading of rearsuspension 40 and protecting shock absorber 42 from “tire roost” (i.e.,protecting shock absorber 40 from being exposed to soil and water flungupward by the bicycle tires).

In the illustrated embodiment a first end 80 of shock absorber 42 iscoupled by means of a pivot 82 to a first support bracket 84 mounted onan upper, forward portion of frame down tube 24. A second end 86 ofshock absorber 42 is coupled by means of a pivoting swing link 88 to asecond support bracket 90 mounted on an upper lower portion of framedown tube 24. More particularly, pivoting swing link 88 has one endcoupled to second support bracket 90 by means of a pivot 92 and anotherend coupled to second end 86 of shock absorber 42.

Linkage 44 couples rear suspension 40 to shock absorber 42. In theembodiment illustrated in FIGS. 3-5, linkage 44 couples second end 86 ofshock absorber 42 to a central portion of rocker arm 50. However, manyother arrangements for operatively coupling rear suspension 40 and shockabsorber 42 may be envisioned, as described below. In the embodiment ofFIGS. 3-5, linkage 44 includes a pair of spaced-apart push linkages 96which straddle seat tube 26. A first end of 98 of each push linkage 96is pivotably connected to second end 86 of shock absorber 42 by means ofa pivot 101 and a second end 100 of each push linkage 96 is pivotablyconnected to a midportion of a corresponding rocker arm element 51 bymeans of a pivot 102. In operation, forward pivoting motion of rockerarm 50 toward seat tube 26 causes a transfer of forces through pushlinkages 96 to shock absorber 42 (FIG. 5(b)). Thus linkage 44 transferssuspension forces received by rear suspension 40 at a location rearwardof seat tube 26 to shock absorber 42 located forward of seat tube 26. Inorder to accomplish this function linkage 44 extends in a planeintersecting the longitudinal axis of seat tube 26.

In an alternative embodiment of the invention linkage 44 may include asingle push linkage 96 (i.e., it is not a requirement of the inventionthat two separate push linkages 96 straddle seat tube 26).

Linkage 44 is sometimes referred to herein as FourX4™ or 4X4™ linkage.This is because each push linkage 96 includes four separate pivots totransfer forces from rear suspension 40 around seat tube 26 to shockabsorber 42, namely pivots 76, 92, 101 and 102. As described above, rearsuspension 40 also employs four different pivot points, namely pivots56, 62, 70 and 76. Thus rear suspension system 12 may be considered dobe a “dual four bar” suspension system. As a result of the relativepositions and spacing of the aforesaid pivots, the special relationshipbetween the various linkages of rear suspension system 12 changessignificantly between the uncompressed riding configuration of FIG. 5(a)and the compressed configuration of FIG. 5(b). For example, as rockerarm link 50 moves forwardly to a more upright orientation extendinggenerally parallel to seat tube 26 as shown in FIG. 5(b), swing link 88is also caused, via push linkages 96, to pivot to a more uprightorientation, thereby causing compression of shock absorber 42.

One notable difference between the present invention and some prior artconfigurations is that in the applicant's design the most forward pivotpoint of rear suspension 40 is located rearward of the longitudinal axisof seat tube 26 rather than on or in front of seat tube 26. Oneadvantage of this design is that the length of chain stay link 46, seatstay link 48 and rocker arm link 50 can be maintained at a normal length(i.e., the length of one or more of such linkages does not need to beincreased in order to connect directly to shock absorber 42 or tosupport structures located forwardly of seat tube 26). By contrast, someprior art designs have comparatively long linkages of swing arms whichresults in a sacrifice of lateral rigidity.

One other important advantage of the present invention is that acontinuous seat tube 26 may be employed. This ensures that seat post hasa sufficient height adjustment range. As used in this patent applicationa “continuous” seat tube 26 refers to a seat tube that extends upwardlyfrom a lower portion of frame 18, such as down tube 24, and is straightand uninterrupted between frame 18 and its upper end. By way ofcontrasting example, FIG. 2 shows an arrangement of the prior art wherethe seat tube is discontinuous (i.e., it is interrupted at its lower endto accommodate a rear shock absorber underneath the seat tube). Asexplained above, such an arrangement restricts the adjustability of theseat post slidable within the seat tube and hence the available range ofseat positions. By way of another example, a seat tube having a lowerportion which is bent to avoid contact with the rear suspension wouldalso considered to be “interrupted” and not continuous since the bend inthe tube would impede a full range of adjustment of the seat postslidable therein.

Further, as shown best in FIG. 6, in the applicant's invention theposition and angle of continuous seat tube 26 has been engineered toensure that a rider seated on seat 34 is in an optimum biomechancialposition. In the following discussion seat tube 26 is assumed to extendin the same plane as the remainder of bicycle frame 18 (i.e., in asubstantially vertical plane when bicycle 10 is in a normal ridingorientation). The position and angle of seat tube 26 is determined bytwo primary constraints. First, seat tube 26 is positioned so that itslongitudinal axis extends tangentially relative to the most forwardlyintrusive position of rear wheel 14 and rear suspension 40 (FIGS. 5(b)and 6). As used herein “forwardly intrusive” refers to the most forwardposition of rear wheel 14 and/or rear suspension 40 when rear suspensionsystem 12 is under full compression. In this case, rear wheel 14 is in araised and forward position and seat stay link 48 and rocker arm link 50are pivoted forwarded (FIG. 5(b)). For example, comparing FIGS. 5(a) and5(b), seat stay arch 53 and pivots 70 have moved forwardly and upwardlyto a position closely proximate to seat tube 26.

Secondly, the longitudinal axis of seat tube 26 is such that when seat34 is raised or lowered to the desired height the rider is positioned ina biomechanically efficient position. As discussed above, seat 34ordinarily needs to be raised to allow for effective pedalingperformance when climbing hills and traversing non-technical terrain.Seat 34 also needs to be lowered substantially (usually by 4-8 inches ormore depending on the rider's height and body proportions) so that therider can safely and effectively traverse difficult or challengingterrain and obstacles, for example during aggressive freeriding. Inparticular, it is desirable to move seat 34 to a lower forward positionso that it does not interfere with preferred downhill riding positions(when traversing steep downhill slopes or other challenging terrain, itis often desirable for the rider's “bottom” to be lowered and movedrearwardly to alter the rider's center of gravity).

As shown in FIG. 6, a “region of biomechanical efficiency” is shown inhatched lines which denotes a preferred range of positions of seat tube26 (and hence seat 34). In this example, the bottom boundary of theregion is the longitudinal axis of frame top tube 22; the front boundaryof the region is a line that is 5° from a vertical plane passing throughthe axis of bottom bracket 35 and 850 from a horizontal plane centeredon the bottom bracket axis; the rear boundary is of the region is a linethat is 30° from a vertical plane passing through the axis of bottombracket 35° and 60° from a horizontal plane centered on the bottombracket axis; and the top boundary is a line formed by the intersectionof the plane of the bicycle front frame and a horizontal plane whichincludes a point defined by the intersection of the longitudinal axes oftop tube 22 and head tube 28.

As should be apparent from FIG. 6, it is important that the longitudinalaxis of seat tube 26 extend within the region of biomechanicalefficiency at a location that does not interfere with rear wheel 14 orrear suspension 40 when such components are in their most forwardposition (i.e., when rear shock absorber 42 is under full compression).As explained above, the position of seat 34 is largely determined by theangle of seat tube 26 (although seat 34 may be adjustable forwardly andrearwardly to a limited extent on rails (not shown) mounted on the topof seat post 32). Further, the actual position of seat 34 may be abovethe above-defined region of biomechanical efficiency, especially whenseat 34 is in the most raised position for hill climbing, but thelongitudinal axis of seat tube 26 preferably extends through thisregion. In the illustrated embodiment the longitudinal axis of seat tube26 extends at an angle of about 58° relative to a horizontal plane (asdefined above). Since the longitudinal axis of seat tube 26 is notcoincident with the axis of bottom bracket 35, but is instead offsetforwardly as described above, this corresponds to an effective seat tubeangle of about 72° relative to the horizontal plane as measured frombottom bracket 35 (which support's the bicycle pedals). In oneembodiment of the invention, the preferred actual angular range of seattube 26 as measured above is between about 50-70° which corresponds to apreferred effective angular range of between about 60-85° as measuredabove. If the longitudinal axis of seat tube 26 is too sharply inclined(e.g., having an actual angle less than about 45° relative to ahorizontal plane), this may result in rear suspension 40 contacting seattube 26, seat post 32 or seat 34 when rear suspension 40 is in its mostforwardly intrusive position, particularly in the case of long travelrear suspension systems. Further, such a sharply inclined seat tube 26would restrict the amount of space available forward of seat tube 26 toaccommodate rear shock absorber 42. Conversely, if the orientation isoverly upright (e.g., if the longitudinal axis of seat tube 26 extendsat an actual angle more than about 75° degrees relative to a horizontalplane), then the rider will not be an optimum biomechanical position foruphill pedaling.

As explained above, the principles of the present invention may apply tomany alternative bicycle configurations, including bicycles havingdifferent frame 18 and/or rear suspension 40 configurations. Someexamples of alternative arrangements are shown schematically in FIGS.6-10. FIG. 6-7 illustrates schematically the embodiment of FIGS. 3-5where linkage 44 is driven by rocker arm link 50 (FIG. 6 showing thisconfiguration in a compressed configuration and FIG. 7 showing the sameconfiguration in an uncompressed configuration).

FIG. 8 illustrates an alternative arrangement where linkage 44 is drivenby chain stay link 46. In particular, instead of coupling linkage 44 torocker arm 50, pivot 102 is located rearwardly of rocker arm 50 and iscoupled by means of linkages 110 and 112 to pivots 56 and 62 located onopposite ends of chain stay link.

FIG. 9 illustrates a further alternative arrangement where linkage 44 isdriven by a single pivot suspension system employing a longer swing arm(i.e., chain stay link 46). In this arrangement rear wheel 14 is mountedat a fixed location on chain stay link 46 which is in turn connecteddirectly to pivot 54. In this embodiment pivot 62 is positioned at oneend of seat stay link 48 and linkage 44 is driven by a combination ofrocker link 50 and seat stay link 48.

FIG. 10 illustrates a walking beam four bar linkage utilizing theinvention. In this case a modified walking beam linkage 114 extendsbetween an upper end of seat stay link 48 and a pivot 116 mounted onseat tube 26. Linkage 44 employs a push linkage 96 having one endpivotably coupled to walking beam linkage 114 by means of a pivot 115and another end coupled to triangular A-links 116 fixed to frame 18. Atleast one segment of A-links 116 intersects a plane parallel to thelongitudinal axis of seat tube 26 to couple push linkage 96 to shockabsorber 42. As in other embodiments of the invention, linkage 44functions as an intermediate coupling for transferring rear suspensionforces around seat tube 26 to shock absorber 42 located at a positionforwardly of seat tube 26.

As will be appreciated by a person skilled in the art, many otheralternative variations of linkage 44 may be envisioned for use inassociation with different rear suspension designs.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. Accordingly, the scope of the invention is to beconstrued in accordance with the substance defined by the followingclaims.

1. (canceled)
 2. A dual four bar suspension system for a bicycle thatincludes a frame, a rear wheel, and a rear shock absorber, the dual fourbar suspension comprising: a four bar rear suspension that pivotallycouples the rear wheel to the frame and that comprises: a chain staylink pivotally coupled to the frame; a seat stay link pivotally coupledto the chain stay link; and a rocker arm link pivotally coupled to theseat stay link and pivotally coupled to the frame; and a four barlinkage assembly that couples the rear suspension to the rear shockabsorber to transfer forces therebetween, the four bar linkage assemblycomprising: a first link pivotally coupled to the rocker arm link; and asecond link pivotally coupled to the first link and pivotally coupled tothe frame; wherein at least one of the first link and the second link ispivotally coupled to the rear shock absorber.
 3. The dual four barsuspension system of claim 2, wherein the four bar linkage assemblyfurther comprises a first pivot connector that couples the second linkto the frame, a second pivot connector that couples the rocker arm linkto the frame, a third pivot connector that couples the first link to therocker arm link, and a fourth pivot connector that couples the firstlink to the rear shock absorber.
 4. The dual four bar suspension systemof claim 2, wherein the four bar linkage assembly further comprises afirst pivot connector that couples the second link to the frame, asecond pivot connector that couples the rocker arm link to the frame, athird pivot connector that couples the first link to the rocker armlink, and a fourth pivot connector that couples the second link to therear shock absorber.
 5. The dual four bar suspension system of claim 2,wherein the four bar linkage assembly straddles a seat tube of thebicycle.
 6. The dual four bar suspension system of claim 2, wherein therear shock absorber is disposed entirely forwardly of a seat tube of thebicycle.
 7. The bicycle comprising the dual four bar suspension systemof claim
 2. 8. The dual four bar suspension system of claim 2, wherein:the rocker arm link comprises a first end pivotally coupled to the seatstay link and a second end pivotally coupled to the frame; and the firstlink is pivotally coupled to the rocker arm link at an intermediatelocation between the first and second ends of the rocker arm link.
 9. Arear suspension system for a bicycle that has a rear wheel and a framethat includes a seat tube that has a longitudinal axis, the rearsuspension system comprising: a rear suspension that couples the wheelto the frame; a rear shock absorber coupled to the frame; and a linkagethat couples the rear suspension to the shock absorber to transferforces therebetween, wherein the linkage comprises a four bar linkageassembly comprising at least four separate pivot connectors, wherein atleast one of the pivot connectors couples the linkage to the frame andat least one other of the pivot connectors couples the linkage to therear suspension.
 10. The rear suspension system of claim 9, wherein theat least one of the pivot connectors that couples the linkage to theframe is located forwardly of the seat tube.
 11. The rear suspensionsystem of claim 9, wherein the at least one other of the pivotconnectors that couples the linkage to the rear suspension is locatedrearwardly of the seat tube.
 12. The rear suspension system of claim 9,wherein the four bar linkage assembly comprises a first link and asecond link which cooperate to operatively connect the at least one ofthe pivot connectors to the at least one other of the pivot connectors.13. The rear suspension system of claim 12, wherein the first and secondlinks are non-rigidly coupled together and are movable relative to oneanother.
 14. The rear suspension system of claim 9, wherein the secondlink is located forwardly of the seat tube.
 15. The bicycle comprisingthe rear suspension system of claim
 9. 16. A rear suspension system fora bicycle that has a rear wheel and a frame that includes a seat tubewith a longitudinal axis, the rear suspension system comprising: a rearsuspension that pivotally couples the wheel to the frame, wherein therear suspension controls a path traversed by the rear wheel as the rearsuspension moves between relatively uncompressed and compressedpositions; a rear shock absorber coupled to the frame; and a linkagethat couples the rear suspension to the shock absorber to transferforces therebetween, wherein: the linkage is pivotably coupled to theshock absorber and comprises a first link coupled to the rear suspensionand a second link coupled to the rear shock absorber; the first andsecond links are operatively coupled together and are movable relativeto one another to control progression of the shock absorber as thesuspension moves between the relatively uncompressed and compressedpositions; and the first link of the linkage is pivotably coupled to therear suspension.
 17. The rear suspension system of claim 16, wherein thelinkage comprises a four bar linkage assembly comprising at least fourseparate pivot connectors.
 18. The rear suspension system of claim 17,wherein the four bar linkage assembly further comprises at least aportion of a rocker arm link, the rocker arm link included in the rearsuspension.
 19. The rear suspension system of claim 16, wherein thelinkage controls movement of the rear wheel and the rear suspensionthrough a range of vertical travel of the rear wheel of at least 4inches.
 20. The rear suspension system of claim 19, wherein the linkagecontrols movement of the rear wheel and the rear suspension through arange of vertical travel between 5 inches and 10 inches.
 21. The bicyclecomprising the rear suspension system of claim
 16. 22. The bicycle ofclaim 21, wherein an effective angle of the seat tube is in a rangebetween 60 degrees and 85 degrees.
 23. The bicycle of claim 21, wherein:the frame includes a top tube and a down tube coupled to the seat tube;and the seat tube is a continuous seat tube that extends along thelongitudinal axis from the top tube to the down tube.
 24. The bicycle ofclaim 23, wherein: the longitudinal axis of the seat tube extends withina region of biomechanical efficiency; the region of biomechanicalefficiency has: a bottom boundary defined by a longitudinal axis of thetop tube; a front boundary defined by a line that is 5° from a verticalplane that passes through an axis of the bottom bracket of the bicycle;a rear boundary defined by a line that is 30° from the vertical planethat passes through the axis of the bottom bracket; and a top boundarydefined by a line formed by an intersection of the frame with ahorizontal plane which includes a point defined by an intersection ofthe longitudinal axis of the top tube with a head tube of the frame. 25.The bicycle of claim 21, wherein the longitudinal axis of the seat tubeintersects a bottom tube of the bicycle at a location spaced forwardlyand upwardly from a bottom bracket of the bicycle.